Eclipse Combustion Engineering Guide - Burnerparts

LIQUID HEATING – BURNER SIZING GUIDELINES
I. Tank Heating
To determine the immersion burner size for heating a
liquid tank, conduct two heat balances–one for heatup
requirements, the other for steady-state operating
requirements. Use the larger of the two Btu inputs
obtained from these calculations.
A. Heat Balance – Heatup Requirements
1.Heat to water
Btu/hr = Lb water x temperature rise, °F
heatup time required, hr
or
Btu/hr = 8.3 x gallons water x temperature rise, °F
heatup time required, hr
or
Btu/hr = 62.4 x cu ft water x temperature rise, °F
heatup time required, hr
Common practice allows the following heatup
times for various size tanks:
Tank Capacity Heatup
Gallons Cu Ft Time, hr
0-375 0-50 2
375-750 50-100 4
750-1500 100-200 6
Over 1500 Over 200 8
2.Surface losses – evaporation & radiation
Btu/hr = Exposed bath surface x heat loss
from Table 1.
3.Tank wall losses
Btu/hr = Total sq ft of tank walls & bottom x wall
loss from Table 1.
4.Tank heat storage
Btu/hr =
Total sq ft, tank walls & bottom x storage, Table 1.
heatup time required, hr
5.Total heatup requirements
Heat to water
+ Surface losses
+ Tank wall losses
+ Tank heat storage
= Total heatup requirement
47
B. Heat Balance – Steady State Heat Requirements
1.Heat to workload
Btu/hr =
Lb of work processed x
hr
specific heat x temperature rise, °F
(Work weight must include all baskets & fixtures)
Specific heat of steel is 0.14 Btu/lb - °F.
See pages 37 to 39 for other materials.
2.Surface losses – evaporation & radiation
Same as Step A.2.
3.Tank wall losses
Same as Step A.3.
4.Heat to makeup water
Btu/hr =
makeup rate, gal/hr x 8.3 x temperature rise, °F
5.Total steady state heat requirement
Heat to workload
+ Surface losses
+ Tank wall losses
+ Heat to makeup water
= Total steady state requirement
C. Compare the heat requirements calculated in
Steps A.5 and B.5. Select the larger of the two .
(This is the net hourly input to the tank.)
D. Gross Heat Input (Burner Firing Rate)
Gross Input, Btu/hr = Net Input from A.5 or B.5 x 100
% Efficiency required
Efficiency is a function of immersion tube
length and burner firing rate. 70% is a commonly
used efficiency rating.
E. Immersion Tube Sizing
See burner manufacturer’s product literature
for tube sizing recommendations.
Table 1. Tank losses & storage
Surface Losses, Wall Losses, Btu/sq ft-hr Heat Storage,
Liquid Btu/sq ft-hr Btu/sq ft
Temperature, Evapor- Radia- Insulation Thickness Steel Thickness
°F ation* tion Total* None 1" 2" 3" 1/8" 1/4"
90 80 50 130 50 12 6 4 21 42
100 160 70 230 70 15 8 6 28 56
110 240 90 330 90 19 10 7 35 70
120 360 110 470 110 23 12 9 42 84
130 480 135 615 135 27 14 10 49 98
140 660 160 820 160 31 16 12 56 112
150 860 180 1040 180 34 18 13 63 126
160 1100 210 1310 210 38 21 15 70 140
170 1380 235 1615 235 42 23 16 77 154
180 1740 260 2000 260 46 25 17 84 168
190 2160 290 2450 290 50 27 19 91 182
200 2680 320 3000 320 53 29 20 98 196
210 3240 360 3590 360 57 31 22 105 210
220 4000 420 4420 380 62 33 23 112 224
250 — 510 — 510 70 40 25 133 266
275 — 600 — 600 81 45 29 151 301
300 — 705 — 705 92 51 33 168 336
325 — 850 — 850 103 57 36 186 371
350 — 990 — 990 114 63 40 203 406
400 — 1335 — 1335 138 75 49 238 476
*Water or water-based solutions only.